package main

import (
	"bufio"
	"fmt"
	"os"
)

type FastScanner struct {
	r *bufio.Reader
}

func NewFastScanner() *FastScanner {
	return &FastScanner{r: bufio.NewReaderSize(os.Stdin, 1<<20)}
}

func (fs *FastScanner) NextInt() int {
	sign, val := 1, 0
	c, _ := fs.r.ReadByte()
	for (c < '0' || c > '9') && c != '-' {
		c, _ = fs.r.ReadByte()
	}
	if c == '-' {
		sign = -1
		c, _ = fs.r.ReadByte()
	}
	for c >= '0' && c <= '9' {
		val = val*10 + int(c-'0')
		c, _ = fs.r.ReadByte()
	}
	fs.r.UnreadByte()
	return sign * val
}

func main() {
	in := NewFastScanner()
	out := bufio.NewWriterSize(os.Stdout, 1<<20)
	defer out.Flush()

	n := in.NextInt()
	p := make([]int, n+1)
	c := make([]int, n+1)
	hasRespectingChild := make([]bool, n+1)

	for i := 1; i <= n; i++ {
		p[i] = in.NextInt()
		c[i] = in.NextInt()
	}

	for i := 1; i <= n; i++ {
		if p[i] != -1 && c[i] == 0 {
			hasRespectingChild[p[i]] = true
		}
	}

	first := true
	for i := 1; i <= n; i++ {
		if p[i] != -1 && c[i] == 1 && !hasRespectingChild[i] {
			if !first {
				fmt.Fprint(out, " ")
			}
			first = false
			fmt.Fprint(out, i)
		}
	}

	if first {
		fmt.Fprint(out, -1)
	}
	fmt.Fprintln(out)
}